User Guide

PMP 450 Planning Guide
The IP address is essential for data delivery through a router interface. Address Resolution Protocol (ARP)
correlates MAC addresses to IP addresses.
For communications to outside the network segment, ARP reads the network gateway address of the router
and translates it into the MAC address of the router. Then the communication is sent to MAC address (physical
network interface card) of the router.
For each router between the sending module and the destination, this sequence applies. The ARP correlation is
stored until the ARP cache times out.
Allocating subnets
The subnet mask is a 32-bit binary number that filters the IP address. Where a subnet mask contains a bit set
to 1, the corresponding bit in the IP address is part of the network address.
Example IP address and subnet mask
In Figure 31 Example of IP address in Class B subnet the first 16 bits of the 32-bit IP address identify the
network:
Figure 31 Example of IP address in Class B subnet
Octet 1 Octet 2 Octet 3 Octet 4
IP address 169.254.1.1 10101001 11111110 00000001 00000001
Subnet mask 255.255.0.0 11111111 11111111 00000000 00000000
In this example, the network address is 169.254, and 2
16
(65,536) hosts are addressable.
Selecting non-routable IP addresses
The factory default assignments for network elements are
• unique MAC address
• IP address of 169.254.1.1
• subnet mask of 255.255.0.0
• network gateway address of 169.254.0.0
For each radio and CMMmicro and CMM4, assign an IP address that is both consistent with the IP addressing
plan for your network and cannot be accessed from the Internet. IP addresses within the following ranges are
not routable from the Internet, regardless of whether a firewall is configured:
• 10.0.0.0 – 10.255.255.255
• 172.16.0.0 – 172.31.255.255
• 192.168.0.0 – 192.168.255.255
You can also assign a subnet mask and network gateway for each CMMmicro and CMM4.
pmp-0047 (March 2014)
1-123